Hdu3681Prison Break状压Dp

 

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <climits>
#include <string>
#include <iostream>
#include <map>
#include <cstdlib>
#include <list>
#include <set>
#include <queue>
#include <stack>
using namespace std;
int dx[]={0,0,-1,1};
int dy[]={-1,1,0,0};
int vis[44][44];int dis[44][44];int Hash[1111];int Map[44][44];char str[44][44];
int len;int n,m;int Begin;
int state[1000];
const int INF=0xfffffff;
int dp[1<<17][17];
int Fin;
int Ma(int a,int b)
{
    return a>b?a:b;
}
void bfs(int x,int y)
{
    queue<int > q;
    q.push(x*m+y);
    memset(dis,0,sizeof(dis));
    memset(vis,0,sizeof(vis));
    vis[x][y]=1;dis[x][y]=0;
    while(!q.empty()){
        int cur=q.front();q.pop();
        int xx= cur/m;int yy=cur%m;
        if(~Hash[cur]){
            Map[Hash[x*m+y]][Hash[cur]]= Map[Hash[cur]][Hash[x*m+y]]=dis[xx][yy];
        }
        for(int i=0;i<4;i++){
            int x1=xx+dx[i];int y1=yy+dy[i];
            if(x1>=0&&x1<n&&y1>=0&&y1<m&&!vis[x1][y1]&&str[x1][y1]!='D'){
                vis[x1][y1]=1; dis[x1][y1]=dis[xx][yy]+1;
                q.push(x1*m+y1);
            }
        }
    }
}// 建图

int gao(int mid)
{
    memset(dp,-1,sizeof(dp));
    dp[1<<Begin][Begin] = mid;
    int gg=(1<<len);
    for(int i=0;i<gg;i++){
        for(int j=0;j<len;j++){
            if(dp[i][j]==-1) continue;
            if((i&(1<<j))==0) continue;
            if((i&Fin)==Fin){
                return 1;
            }
            for(int k=0;k<len;k++){
                if((i&(1<<k))) continue;
                if(Map[j][k]==-1||dp[i][j]<Map[j][k]) continue;
                dp[i|(1<<k)][k]=Ma(dp[i|(1<<k)][k],dp[i][j]-Map[j][k]);
                if(state[k]) dp[i|(1<<k)][k]=mid;
            }
        }
    }
    return 0;
} 


int main()
{
    while(cin>>n>>m,n||m){
        memset(state,0,sizeof(state));
        memset(Hash,-1,sizeof(Hash));
        memset(Map,-1,sizeof(Map));
        Fin = 0;len=0;
        for(int i=0;i<n;i++){
            scanf("%s",str[i]);
            for(int j=0;j<m;j++){
                if(str[i][j]=='S'||str[i][j]=='D') continue;
                Hash[i*m+j]=len;
                if(str[i][j]=='F') Begin= len,Fin|=(1<<len);
                if(str[i][j]=='G') state[len]=1;
                if(str[i][j]=='Y') Fin|=(1<<len);
                len++;
            }
        }
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++)
            if(~Hash[i*m+j]){
                bfs(i,j);
            }
        }
        int l = 0;int r=n*m+10;int gg=-1;
        while(l<=r){
            int mid= (l+r)>>1;
            if(gao(mid)){
                gg=mid;r=mid-1;
            }
            else l=mid+1;
        }
        printf("%d\n",gg);
    }
    return 0;
}